Coatings

15 pages, 4121 KiB

Open AccessFeature PaperArticle

Short- and Long-Term Wettability Evolution and Corrosion Resistance of Uncoated and Polymer-Coated Laser-Textured Steel Surface

by Marjetka Conradi, Tina Sever, Peter Gregorčič and Aleksandra Kocijan

Coatings 2019, 9(9), 592; https://doi.org/10.3390/coatings9090592 - 19 Sep 2019

Cited by 30 | Viewed by 4169

Abstract

We present the results of one year observation of wetting and corrosion properties of nanosecond fiber laser-textured stainless steel, uncoated and coated with epoxy or FAS (fluoroalkylsilane)-TiO₂/epoxy. A comparative study was performed on samples kept under ambient conditions and in reduced [...] Read more.

We present the results of one year observation of wetting and corrosion properties of nanosecond fiber laser-textured stainless steel, uncoated and coated with epoxy or FAS (fluoroalkylsilane)-TiO₂/epoxy. A comparative study was performed on samples kept under ambient conditions and in reduced air pressure and humidity. The results show the ability to induce wettability conversion from initially superhydrophilic to final superhydrophobic state either indirectly by ageing the uncoated laser-textured surface or directly by application of FAS-TiO₂/epoxy coating. The storage conditions significantly influenced the wettability development of uncoated laser-textured steel, i.e., the process of ageing was slowed down in reduced air pressure and humidity. Detailed surface chemical analysis revealed that adsorption of the organic matters from the surrounding media influences the wettability conversion and ageing. However, the ageing of the coated surfaces was not affected by the storage conditions. Corrosion stability of uncoated laser-textured surfaces was enhanced over time due to the wettability transition, depending on their morphology. Coatings represent a superior barrier over the texture and wettability with the stable long-term surface protection against aggressive media. Full article

(This article belongs to the Special Issue Anticorrosion Protection of Nonmetallic and Metallic Coatings)

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12 pages, 4119 KiB

Open AccessArticle

Influence of Charge Carriers Concentration and Mobility on the Gas Sensing Behavior of Tin Dioxide Thin Films

by Ruiwu Li, Yanwen Zhou, Maolin Sun, Zhen Gong, Yuanyuan Guo, Fayu Wu, Weijuan Li and Wutong Ding

Coatings 2019, 9(9), 591; https://doi.org/10.3390/coatings9090591 - 18 Sep 2019

Cited by 38 | Viewed by 3975

Abstract

In order to investigate function of carrier behavior on gas-sensing properties, tin oxide-based films with different carrier concentration and mobility were obtained, by magnetron sputtering from the powder target, which was followed by further oxygen-management though the annealing treatment. The microstructure, surface morphology, [...] Read more.

In order to investigate function of carrier behavior on gas-sensing properties, tin oxide-based films with different carrier concentration and mobility were obtained, by magnetron sputtering from the powder target, which was followed by further oxygen-management though the annealing treatment. The microstructure, surface morphology, electrical properties and gas sensitivity were characterized by XRD, Raman spectrum, photoluminescence spectrum, atomic force microscope, the hall effect system and electrochemical workstation, respectively. The results showed that all SnO₂-based films had a tetragonal rutile phase with (101) preferred orientation. The introduction of fluorine and regulation of oxygen vacancies tuned carrier concentration from 10¹⁵/cm³ to 10²¹/cm³ and mobility from 10² cm²/V·s to 10⁻¹ cm²/V·s. The decreasing carrier concentration as well as increasing mobility had a positively important function to improve the sensitivity of SnO₂-based films. The air-annealed SnO₂ film with lowest carrier concentration had a maximum sensitivity of R = 5.0, while vacuum-annealed SnO₂:F film with the highest carrier concentration being the minimum sensitivity. This puts forward a novel reference for the design and application of SnO₂-based gas sensing films. Full article

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12 pages, 3906 KiB

Open AccessArticle

Surface Functionalization of Activated Carbon with Phosphonium Ionic Liquid for CO₂ Adsorption

by Xiaodong He, Jiamei Zhu, Hongmin Wang, Min Zhou and Shuangquan Zhang

Coatings 2019, 9(9), 590; https://doi.org/10.3390/coatings9090590 - 18 Sep 2019

Cited by 31 | Viewed by 4308

Abstract

Immobilization of phosphonium ionic liquid (IL) onto activated carbon (AC) was synthesized via grafting and impregnated methods, and the modified materials were analyzed via Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, thermal gravity analysis, scanning electron microscope, pore structure and CO₂/N₂ [...] Read more.

Immobilization of phosphonium ionic liquid (IL) onto activated carbon (AC) was synthesized via grafting and impregnated methods, and the modified materials were analyzed via Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction, thermal gravity analysis, scanning electron microscope, pore structure and CO₂/N₂ adsorption selectivity. The effect of the gas flow rate (100–500 mL/min) and adsorption pressure (0.2–0.6 MPa) on the dynamic adsorption behavior of mixture gas containing 15 vol.% CO₂ and 85 vol.% N₂ was explained using a breakthrough method. By analyzing the breakthrough curves, the adsorption capacity was determined. The results show that surface functionalization of activated carbon with phosphonium ionic liquid is conducive to improving CO₂/N₂ selectivity, especially ionic liquid-impregnated film. The different adsorption behaviors of impregnated and grafted adsorbents are observed under various conditions. The grafted AC had better CO₂ adsorption and mass transfer due to a lower blockage of pores by ionic liquid. Full article

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10 pages, 2889 KiB

Open AccessArticle

Influence of the Growth Ambience on the Localized Phase Separation and Electrical Conductivity in SrRuO₃ Oxide Films

by Hsin-Ming Cheng

Coatings 2019, 9(9), 589; https://doi.org/10.3390/coatings9090589 - 18 Sep 2019

Cited by 1 | Viewed by 3608

Abstract

Perovskite SrRuO₃ (SRO) epitaxial thin films grown on SrTiO₃ (STO) (001) have been synthesized using pulsed laser deposition (PLD) under a series of oxygen pressures. High quality and conductive SRO thin films on STO have been achieved at 10⁻¹ Torr [...] Read more.

Perovskite SrRuO₃ (SRO) epitaxial thin films grown on SrTiO₃ (STO) (001) have been synthesized using pulsed laser deposition (PLD) under a series of oxygen pressures. High quality and conductive SRO thin films on STO have been achieved at 10⁻¹ Torr oxygen pressure with the epitaxial relation of (110)<001>_SrRuO₃//(001)<010>_SrTiO₃. The lattice parameters of the thin films exhibit huge expansion by reducing the ambience (~10⁻⁷ Torr) during deposition, and the resistance increases by about two orders higher as compared with the low oxide pressure ones. The rise of resistivity can be ascribed to not only the deficiency of Ru elements but also the phase transformation inside SRO thin films. The correlation of growth ambience on the structural transition and corresponding resistivity of epitaxial oxide thin films have been explicitly investigated. Full article

(This article belongs to the Special Issue Functional Oxide Thin Films and Nanostructures: Growth, Properties, and Applications)

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17 pages, 9113 KiB

Open AccessArticle

Tribological Performance of PVD Film Systems Against Plastic Counterparts for Adhesion-Reducing Application in Injection Molds

by Wolfgang Tillmann, Nelson Filipe Lopes Dias, Dominic Stangier and Nikolai Gelinski

Coatings 2019, 9(9), 588; https://doi.org/10.3390/coatings9090588 - 17 Sep 2019

Cited by 11 | Viewed by 4405

Abstract

The deposition of physical vapor deposition (PVD) hard films is a promising approach to enhance the tribological properties of injection molds in plastic processing. However, the adhesion is influenced by the pairing of PVD film and processed plastic. For this reason, the friction [...] Read more.

The deposition of physical vapor deposition (PVD) hard films is a promising approach to enhance the tribological properties of injection molds in plastic processing. However, the adhesion is influenced by the pairing of PVD film and processed plastic. For this reason, the friction behavior of different PVD films against polyamide, polypropylene, and polystyrene was investigated in tribometer tests by correlating the relation between the roughness and the adhesion. It was shown that the dispersive and polar surface energy have an impact on the work of adhesion. In particular, Cr-based nitrides with a low polar component exhibit the lowest values ranging from 65.5 to 69.4 mN/m when paired with the polar polyamide. An increased roughness leads to a lower friction due to a reduction of the adhesive friction component, whereas a higher work of adhesion results in higher friction for polyamide and polypropylene. Within this context, most Cr-based nitrides exhibited coefficients of friction below 0.4. In contrast, polystyrene leads to a friction-reducing material transfer. Therefore, a customized deposition of the injection molds with an appropriated PVD film system should be carried out according to the processed plastic. Full article

(This article belongs to the Special Issue Magnetron Sputtering Deposited Thin Films and Its Applications)

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20 pages, 5228 KiB

Open AccessArticle

Synthesis of Silane Functionalized Graphene Oxide and Its Application in Anti-Corrosion Waterborne Polyurethane Composite Coatings

by Chao Chen, Shicheng Wei, Bin Xiang, Bo Wang, Yujiang Wang, Yi Liang and Yue Yuan

Coatings 2019, 9(9), 587; https://doi.org/10.3390/coatings9090587 - 17 Sep 2019

Cited by 46 | Viewed by 6422

Abstract

In this study, novel silane functionalized graphene oxide (PVSQ-GO) composite material is synthesized through the hydrolysis condensation reaction of vinyl triethoxysilane monomers occurred at the surface of graphene oxide. Results obtained from FTIR, Raman, X-ray photoelectronic spectroscopy (XPS), XRD and TGA measurements reveal [...] Read more.

In this study, novel silane functionalized graphene oxide (PVSQ-GO) composite material is synthesized through the hydrolysis condensation reaction of vinyl triethoxysilane monomers occurred at the surface of graphene oxide. Results obtained from FTIR, Raman, X-ray photoelectronic spectroscopy (XPS), XRD and TGA measurements reveal that polyvinyl sesquisiloxane microspheres adhere to graphene oxide lamellae in the form of chemical bonds. Meanwhile, it is intuitive that abundant polyvinyl sesquisiloxane microspheres stick to the surface of graphene oxide and increase the thickness of the flake. Modified graphene oxide changes from hydrophilicity to hydrophobicity were owing to the existence of polyvinyl sesquisiloxane microspheres on the surface of graphene oxide (GO). PVSQ-GO composite exhibited good dispersion in eco-friendly waterborne polyurethane coating. Electrochemical impedance spectroscopy manifested that the anti-corrosion performance of waterborne polyurethane (WPU) coating embedded at 0.5 wt.% PVSQ-GO composite improved effectively. Tafel curves reveal that 0.5 wt.% PVSQ-GO/WPU coating specimen shows the lowest corrosion rate of 8.95 × 10⁻⁵ mm/year when compared with the other coating specimens. The good anti-corrosion abilities of PVSQ-GO composite coating can be interpreted as the good compatibility between PVSQ-GO composite and waterborne polyurethane, however, the intrinsic hydrophobicity of PVSQ-GO composite is beneficial to inhibit the permeation of corrosive medium and thus slows down the corrosion rate. Full article

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11 pages, 9405 KiB

Open AccessArticle

High Intensity Laser Induced Reverse Transfer: Solution for Enhancement of Biocompatibility of Transparent Biomaterials

by Naghmeh Safaie, Holly Jones-Taggart and Amirkianoosh Kiani

Coatings 2019, 9(9), 586; https://doi.org/10.3390/coatings9090586 - 17 Sep 2019

Cited by 3 | Viewed by 2847

Abstract

Bioactive glass is used extensively in biomedical applications due to its quality and effectiveness in tissue regeneration. Bioactive glasses are able to interact with biological systems and can be used in humans to improve tissue regeneration without any side effects. Bioactive glass is [...] Read more.

Bioactive glass is used extensively in biomedical applications due to its quality and effectiveness in tissue regeneration. Bioactive glasses are able to interact with biological systems and can be used in humans to improve tissue regeneration without any side effects. Bioactive glass is a category of glasses that maintain good contact with body organs and remain biocompatible for a long time after implementation. They have the potential to form a hydroxyapatite surface as a biocompatible layer after immersion in body fluid. In this research, glass biocompatibility was modified using a deposition method called the high intensity laser induced reverse transfer (HILIRT) method and they were utilized as enhanced-biocompatibility bioactive glass (EBBG) with a correspondent nanofibrous titanium (NFTi) coating. HILIRT is a simple ultrafast laser method for improving implants for biomedical applications and provides a good thin film of NFTi on the glass substrate that is compatible with human tissue. The proposed method is a non-chemical method in which NFTi samples with different porosities and biocompatibilities are synthesized at various laser parameters such as power and frequency. Physical properties and cell compatibility and adhesion of these NFTi before and after immersion in simulated body fluid (SBF) were compared. The results indicate that increasing laser intensity and frequency leads to more NFTi fabrication on the glass with no toxicity and better cell interaction and adhesion. Full article

(This article belongs to the Special Issue Micro- and Nano-Coatings for Technological and Biomedical Applications)

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13 pages, 12269 KiB

Open AccessArticle

Crack Healing in Mullite-Based EBC during Thermal Shock Cycle

by Hyoung-IL Seo, Daejong Kim and Kee Sung Lee

Coatings 2019, 9(9), 585; https://doi.org/10.3390/coatings9090585 - 17 Sep 2019

Cited by 9 | Viewed by 3713

Abstract

Crack healing phenomena were observed in mullite and mullite + Yb₂SiO₅ environmental barrier coating (EBC) materials during thermal shock cycles. Air plasma spray coating was used to deposit the EBC materials onto a Si bondcoat on a SiC_f/SiC [...] Read more.

Crack healing phenomena were observed in mullite and mullite + Yb₂SiO₅ environmental barrier coating (EBC) materials during thermal shock cycles. Air plasma spray coating was used to deposit the EBC materials onto a Si bondcoat on a SiC_f/SiC composite substrate. This study reveals that unidirectional vertical cracks (mud cracks) formed after several thermal shock cycles; however, the cracks were stable for 5000 thermal shock cycles at a maximum temperature of 1350 °C. Moreover, the crack densities decreased with an increasing number of thermal shock cycles. After 3000 thermal shock cycles, cracks were healed via melting of a phase containing SiO₂ phase, which partially filled the gaps of the cracks and resulted in the precipitation of crystalline Al₂O₃ in the mullite. Post-indentation tests after thermal shock cycling indicated that the mullite-based EBC maintained its initial mechanical behavior compared to Y₂SiO₅. The indentation load–displacement tests revealed that, among the materials investigated in the present study, the mullite + Yb₂SiO₅ EBC demonstrated the best durability during repetitive thermal shocks. Full article

(This article belongs to the Special Issue Environmental Barrier Coatings)

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13 pages, 5854 KiB

Open AccessArticle

Investigation of the Oxidation Mechanism of Dopamine Functionalization in an AZ31 Magnesium Alloy for Biomedical Applications

by Arezoo Ghanbari, Fernando Warchomicka, Christof Sommitsch and Ali Zamanian

Coatings 2019, 9(9), 584; https://doi.org/10.3390/coatings9090584 - 16 Sep 2019

Cited by 34 | Viewed by 4193

Abstract

Implant design and functionalization are under significant investigation for their ability to enhance bone-implant grafting and, thus, to provide mechanical stability for the device during the healing process. In this area, biomimetic functionalizing polymers like dopamine have been proven to be able to [...] Read more.

Implant design and functionalization are under significant investigation for their ability to enhance bone-implant grafting and, thus, to provide mechanical stability for the device during the healing process. In this area, biomimetic functionalizing polymers like dopamine have been proven to be able to improve the biocompatibility of the material. In this work, the dip coating of dopamine on the surface of the magnesium alloy AZ31 is investigated to determine the effects of oxygen on the functionalization of the material. Two different conditions are applied during the dip coating process: (1) The absence of oxygen in the solution and (2) continuous oxygenation of the solution. Energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) are used to analyze the composition of the formed layers, and the deposition rate on the substrate is determined by molecular dynamic simulation. Electrochemical analysis and cell cultivation are performed to determine the corrosion resistance and cell’s behavior, respectively. The high oxygen concentration in the dopamine solution promotes a homogeneous and smooth coating with a drastic increase of the deposition rate. Also, the addition of oxygen into the dip coating process increases the corrosion resistance of the material. Full article

(This article belongs to the Special Issue Surface Engineering of Light Alloys)

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15 pages, 24315 KiB

Open AccessArticle

Novel Edible Coating with Antioxidant and Antimicrobial Activities Based on Whey Protein Isolate Nanofibrils and Carvacrol and Its Application on Fresh-Cut Cheese

by Qiannan Wang, Hongliang Yu, Bo Tian, Bin Jiang, Jing Xu, Dongmei Li, Zhibiao Feng and Chunhong Liu

Coatings 2019, 9(9), 583; https://doi.org/10.3390/coatings9090583 - 16 Sep 2019

Cited by 52 | Viewed by 6016

Abstract

The composition and properties of edible coatings (ECs) will significantly influence their effects of food preservation. For the first time, whey protein isolates nanofibers (WPNFs), as a novel material with high hydrophobicity and antioxidant activity, combined with carvacrol (CA) as an antimicrobial agent [...] Read more.

The composition and properties of edible coatings (ECs) will significantly influence their effects of food preservation. For the first time, whey protein isolates nanofibers (WPNFs), as a novel material with high hydrophobicity and antioxidant activity, combined with carvacrol (CA) as an antimicrobial agent and glycerol (Gly) as a plasticizer, was used to prepare edible coating (WPNFs-CA/Gly) for preserving fresh-cut Cheddar cheese. The prepared WPNFs and ECs emulsions have been investigated with transmission electron microscopy. Furthermore, the antioxidant activity of ECs emulsions, antimicrobial activity of edible films, and the physical properties of edible films, such as micromorphology, thickness, transparency, and moisture content, have also been evaluated. The weight losses and physical characteristics of both coated and uncoated fresh-cut Cheddar cheese samples have been assessed during storage. The DPPH free radical scavenging rate of WPNFs-CA/Gly emulsion was up to 67.89% and the reducing power was 0.821, which was higher than that of WPI-CA/Gly emulsions. The antimicrobial activity of WPNFs-CA/Gly films was nearly 2.0-fold higher than that of WPNFs/Gly films for the presence of CA. The WPNFs-CA/Gly films had smooth and continuous surfaces, and the transparency reached 49.7% and the moisture content was 26.0%, which was better than that of WPI-CA/Gly films. Furthermore, Cheddar cheese with WPNFs-CA/Gly coatings has shown lower weight losses (15.23%) and better textural properties than those uncoated samples. This in-depth study has provided a valuable and noteworthy approach about the novel edible coating material. Full article

(This article belongs to the Special Issue Edible Films and Coatings: Fundamentals and Applications)

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16 pages, 3318 KiB

Open AccessArticle

Preparation and Characterization of Ultrasound Treated Polyvinyl Alcohol/Chitosan/DMC Antimicrobial Films

by Rui Li, Yue Wang, Jie Xu, Saeed Ahmed and Yaowen Liu

Coatings 2019, 9(9), 582; https://doi.org/10.3390/coatings9090582 - 15 Sep 2019

Cited by 10 | Viewed by 5575

Abstract

In this research, chitosan (CS) and poly (vinyl alcohol) (PVA) were adopted as a material, methacryloyloxyethyl trimethyl ammonium chloride (DMC) was added in various concentrations and was treated ultrasonically for the formation of films with the use of the polymer blending method. The [...] Read more.

In this research, chitosan (CS) and poly (vinyl alcohol) (PVA) were adopted as a material, methacryloyloxyethyl trimethyl ammonium chloride (DMC) was added in various concentrations and was treated ultrasonically for the formation of films with the use of the polymer blending method. The influences exerted by the ultrasonication period on PVA/CS/DMC antimicrobial active materials underwent material characteristic tests. The consequences revealed that at the break of the compound films, ultrasonication raised the elongation and tensile strength on the whole. Ultrasonication further or also enhanced the light transmittance performance and composite films’ barrier property. Furthermore, the compound film with a DMC concentration of 2% had good antibacterial properties, the film’s inhibition rates against Staphylococcus aureus and Escherichia coli after ultrasonication were 79.23% ± 1.92% and 72.31% ± 1.35%, respectively. Full article

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14 pages, 8782 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Antimicrobial Efficacy of Low Concentration PVP-Silver Nanoparticles Deposited on DBD Plasma-Treated Polyamide 6,6 Fabric

by Ana Isabel Ribeiro, Dilara Senturk, Késia Karina Silva, Martina Modic, Uros Cvelbar, Gheorghe Dinescu, Bogdana Mitu, Anton Nikiforov, Christophe Leys, Irina Kuchakova, Mike De Vrieze, António Pedro Souto and Andrea Zille

Coatings 2019, 9(9), 581; https://doi.org/10.3390/coatings9090581 - 14 Sep 2019

Cited by 27 | Viewed by 4969

Abstract

In this study, a low concentration (10 μg·mL⁻¹) of poly(N-vinylpyrrolidone) (PVP)-coated silver nanoparticles (AgNPs) were deposited by spray and exhaustion (30, 70 and 100 °C) methods onto untreated and dielectric barrier discharge (DBD) plasma-treated polyamide 6,6 (PA66) fabric. DBD plasma-treated samples [...] Read more.

In this study, a low concentration (10 μg·mL⁻¹) of poly(N-vinylpyrrolidone) (PVP)-coated silver nanoparticles (AgNPs) were deposited by spray and exhaustion (30, 70 and 100 °C) methods onto untreated and dielectric barrier discharge (DBD) plasma-treated polyamide 6,6 (PA66) fabric. DBD plasma-treated samples showed higher AgNP deposition than untreated ones for all methods. After five washing cycles, only DBD plasma-treated samples displayed AgNPs on the fabric surface. The best-performing method was exhaustion at 30 °C, which exhibited less agglomeration and the best antibacterial efficacy against S. aureus (4 log reduction). For E. coli, the antimicrobial effect showed good results in all the exhaustion samples (5 log reduction). Considering the spray method, only the DBD plasma-treated samples showed some bacteriostatic activity for both strains, but the AgNP concentration was not enough to have a bactericidal effect. Our results suggest DBD plasma may be a low cost and chemical-free method for the preparation of antibacterial textiles, allowing for the immobilization of a very low—but effective—concentration of AgNPs. Full article

(This article belongs to the Special Issue Functional Coatings for Textile Applications)

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10 pages, 2374 KiB

Open AccessArticle

Two-Body and Three-Body Wear Behavior of a Dental Fluorapatite Glass-Ceramic

by Gaoqi Wang, Yunkai Li, Shouren Wang, Xuefeng Yang and Yujing Sun

Coatings 2019, 9(9), 580; https://doi.org/10.3390/coatings9090580 - 13 Sep 2019

Cited by 5 | Viewed by 3313

Abstract

As a veneering porcelain coating of dental prosthesis, two-body and three-body wear behavior of dental glass-ceramic with the main crystalline phase of fluorapatite has not been comprehensively studied. In this work, a self-made fluorapatite glass-ceramic was synthesized and the mechanical and tribological performances [...] Read more.

As a veneering porcelain coating of dental prosthesis, two-body and three-body wear behavior of dental glass-ceramic with the main crystalline phase of fluorapatite has not been comprehensively studied. In this work, a self-made fluorapatite glass-ceramic was synthesized and the mechanical and tribological performances of the glass-ceramic were tested, comparing with a commercial feldspathic glass-ceramic. The friction and wear experiments were performed between disk-shaped glass-ceramics and natural teeth in two-body (dry, water, saliva) and three-body (slurry) modes, respectively. Results showed that good mechanical properties of fluorapatite glass-ceramic can be achieved by the sintering process. In both two-body and three-body modes, the fluorapatite glass-ceramic had a smaller friction coefficient and wear rate and caused less damage on antagonistic teeth than the feldspathic glass-ceramic. The greater mechanical properties give fluorapatite glass-ceramic a better wear resistance and reduce the adhesive wear. Full article

(This article belongs to the Special Issue Micro- and Nano-Coatings for Technological and Biomedical Applications)

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13 pages, 4038 KiB

Open AccessEditor’s ChoiceArticle

Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO₂/Al₂O₃/HfO₂ Triple-Interlayer for Biomedical Implants

by Changzheng Li, Maarten Cauwe, Yang Yang, David Schaubroeck, Lothar Mader and Maaike Op de Beeck

Coatings 2019, 9(9), 579; https://doi.org/10.3390/coatings9090579 - 12 Sep 2019

Cited by 31 | Viewed by 6112

Abstract

Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up [...] Read more.

Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO₂/Al₂O₃/HfO₂ (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al₂O₃, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices. Full article

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15 pages, 43906 KiB

Open AccessArticle

Investigation on the Surface Properties of 5A12 Aluminum Alloy after Nd: YAG Laser Cleaning

by Guodong Zhu, Shouren Wang, Wei Cheng, Gaoqi Wang, Wentao Liu and Yuan Ren

Coatings 2019, 9(9), 578; https://doi.org/10.3390/coatings9090578 - 12 Sep 2019

Cited by 47 | Viewed by 5058

Abstract

The surface of the aluminum alloy is prone to oxidation, which in turn affects the quality of the weld. The 5A12 aluminum alloy was cleaned by acousto-optic Q-switched diode-pumped Nd:YAG laser and the effects of different laser powers and different cleaning speeds on [...] Read more.

The surface of the aluminum alloy is prone to oxidation, which in turn affects the quality of the weld. The 5A12 aluminum alloy was cleaned by acousto-optic Q-switched diode-pumped Nd:YAG laser and the effects of different laser powers and different cleaning speeds on the surface roughness, microstructure, element content, microhardness, residual stress and corrosion resistance of aluminum alloy were investigated. The results show that when the power is 98W and the cleaning speed is 4.1 mm/s, the effect of Nd: YAG laser on the removal of oxide film on 5A12 aluminum alloy surface is the most effective. After laser cleaning, the smoothness and strength of aluminum alloy surface can be effectively improved. However, as a major element in 5A12 aluminum alloy, the content of magnesium decreased. At the same time, the residual tensile stress was generated on the surface of the aluminum alloy after cleaning, and the corrosion resistance slightly decreased. Full article

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9 pages, 1490 KiB

Open AccessArticle

Large-Area Coating of Previtamin D₃ Based on Roll-to-Roll Processing

by Janghoon Park, Yoonki Min, Jongsu Lee, Hakyung Jeong, Youngwook Noh, Kee-Hyun Shin and Dongjin Lee

Coatings 2019, 9(9), 577; https://doi.org/10.3390/coatings9090577 - 11 Sep 2019

Cited by 1 | Viewed by 2821

Abstract

We propose a roll-to-roll process for vitamin D₃ patch production. A solution of 7-dehydrocholesterol is applied to a plastic film by roll-to-roll slot-die coating and dried by a far-infrared lamp. Upon exposure to ultraviolet B irradiation, these films are converted to previtamin [...] Read more.

We propose a roll-to-roll process for vitamin D₃ patch production. A solution of 7-dehydrocholesterol is applied to a plastic film by roll-to-roll slot-die coating and dried by a far-infrared lamp. Upon exposure to ultraviolet B irradiation, these films are converted to previtamin D₃ films. After heat-treating the previtamin D₃ film, high-performance liquid chromatography measurements are performed using commercial vitamin D₃ as a standard sample. The results confirm that vitamin D₃ can be produced by large-area coating and post-treatment processes. Specifically, 3.16 ± 0.746 mg of vitamin D₃ is obtained through ultraviolet B irradiation and heat-treatment of 24.8 ± 1.44 mg of coated 7-dehydrocholesterol. Full article

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13 pages, 1089 KiB

Open AccessFeature PaperArticle

Influence of the Hamaker Constant on the Value of the Critical Thickness of Foam Films

by Dilyana Ivanova-Stancheva

Coatings 2019, 9(9), 576; https://doi.org/10.3390/coatings9090576 - 10 Sep 2019

Cited by 2 | Viewed by 3656

Abstract

The aim of the present study was to check the influence of the Hamaker constant (A(h)) on the calculated critical thickness of foam films. It was done by a comparison between the experimental data of the critical thickness and the theoretically obtained data [...] Read more.

The aim of the present study was to check the influence of the Hamaker constant (A(h)) on the calculated critical thickness of foam films. It was done by a comparison between the experimental data of the critical thickness and the theoretically obtained data with different values of (A(h)), which take part in the equations of Radoev, Scheludko, Manev, and Vrij. We calculated the latter for film thicknesses from 15 to 70 nm based on several equations. We used the experimental data of h_cr (average value of critical thickness and measured once, in the place of a spot appearance) for foam films stabilized by non-ionic surfactant n-dodecyl-β-D-maltoside (C₁₂G₂) or by cationic surfactant n-dodecyl trimethylammonium bromide (C₁₂TAB), as measured by the interferometric method. The foam films were produced from solutions with surfactant concentration at CMC (Critical Micelle Concentration) in the presence of 0.1 M NaBr. For films of C₁₂G₂, the best correspondence was found between measured h_cr (in the spot) and calculated ones by the RShM equation using effective A(h) (introduced by Coons et al.) or Vassilieff’s values, but with a correction for the added electrolyte. For films stabilized by C₁₂TAB, a difference between the measured and theoretically calculated h_cr was found, which was probably due to the nature of the surfactant. Nevertheless, this difference was smallest when calculated h_cr values were obtained with data for Aeff (h) and Vassilieff’s A(h) constant, respectively. Full article

(This article belongs to the Special Issue Thin Liquid Films and Dispersed Systems–from Fundamentals to Applications)

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9 pages, 8530 KiB

Open AccessArticle

Magnetite-Accelerated Corrosion of SA508 Tubesheet Material and Its Effect on Steam Generator Tube Denting

by Geun Dong Song, Jeoh Han, Soon-Hyeok Jeon and Do Haeng Hur

Coatings 2019, 9(9), 575; https://doi.org/10.3390/coatings9090575 - 9 Sep 2019

Cited by 4 | Viewed by 3347

Abstract

The objective of this work is to investigate the magnetite-accelerated corrosion phenomenon of SA508 used as tubesheet material in simulated secondary side environments of pressurized water reactors through immersion and electrochemical tests. The presence of sulfate ions induced the fast growth of a [...] Read more.

The objective of this work is to investigate the magnetite-accelerated corrosion phenomenon of SA508 used as tubesheet material in simulated secondary side environments of pressurized water reactors through immersion and electrochemical tests. The presence of sulfate ions induced the fast growth of a corrosion product layer on SA508, and this phenomenon was accelerated when the SA508 was coupled to magnetite. From the perspective of electrochemical behavior, it was found that SA508 behaves as an anodic member in the coupling system with magnetite, resulting in an increased corrosion rate. Full article

(This article belongs to the Special Issue Corrosion Science and Surface Engineering)

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21 pages, 3220 KiB

Open AccessFeature PaperArticle

Poly (Lactic Acid)/Thermoplastic Starch Films: Effect of Cardoon Seed Epoxidized Oil on Their Chemicophysical, Mechanical, and Barrier Properties

by Rosa Turco, Rodrigo Ortega-Toro, Riccardo Tesser, Salvatore Mallardo, Sofia Collazo-Bigliardi, Amparo Chiralt Boix, Mario Malinconico, Massimo Rippa, Martino Di Serio and Gabriella Santagata

Coatings 2019, 9(9), 574; https://doi.org/10.3390/coatings9090574 - 8 Sep 2019

Cited by 85 | Viewed by 7440

Abstract

In this work, biodegradable films based on poly (lactic acid) (PLA) and corn thermoplastic starch (TPS), additivated with epoxidized cardoon oil plasticizer (ECO) at 3% by weight with respect to PLA mass fraction, were prepared by melt extrusion process and compression molding. The [...] Read more.

In this work, biodegradable films based on poly (lactic acid) (PLA) and corn thermoplastic starch (TPS), additivated with epoxidized cardoon oil plasticizer (ECO) at 3% by weight with respect to PLA mass fraction, were prepared by melt extrusion process and compression molding. The effect of ECO on structural, thermal, mechanical, barrier, and spectral optical properties of the films was investigated. Spectroscopic analysis evidenced the development of physical interaction between oil and polymers, mainly PLA. In addition, no oil migration occurrence was detected after six months of film preparation, as evidenced by oil mass evaluation by precipitation as well as by ¹H-NMR methods, thus highlighting the good inclusion of oil inside the polymeric network. The plasticizing action of the oil induced a lean improvement of the interfacial adhesion between hydrophobic PLA and hydrophilic TPS, particularly accentuated in PLA80_ECO composition, as evidenced by morphological analysis of blend fracture surfaces. TGA data underlined that, differently from TPS-based films, PLA-based systems followed one degradative thermal profile suggesting a slight compatibilization effect of epoxidized oil in these films. The shifting of Tg values, by differential scanning calorimetry (DSC) analysis, indicated a weak miscibility at molecular level. Generally, in the investigated blends, the phase separation between PLA and TPS polymers was responsible for the mechanical properties failing; in particular, the tensile strength evidenced a negative deviation from the rule of mixtures, particularly marked in TPS-based blends, where no physical entanglements occurred between the polymers since their immiscibility even in presence of ECO. The epoxidized oil strongly improved the barrier properties (water vapor permeability (WVP) and oxygen permeability (O₂P)) of all the films, likely developing a physical barrier to water and oxygen diffusion and solubilization. With respect to neat PLA, PL80 and PL80_ECO films evidenced the improvement of surface wettability, due to the presence of polar groups both in TPS (hydroxyl residues) and in epoxidized oil (oxirane rings). Finally, following to the conditioning in climatic chamber at T = 25 °C and RH = 50%, PLA80 film became opaque due to TPS water absorption, causing a light transmittance decreasing, as evidenced by spectral optical analysis. Full article

(This article belongs to the Special Issue Coatings and Interfacial Films for Food Applications—Themed Issue to Celebrate Prof. Raffaele Porta’s Career)

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14 pages, 4400 KiB

Open AccessArticle

Numerical Study on the Optimization of Roll-to-Roll Ultraviolet Imprint Lithography

by Usama Tahir, Muhammad Ahmad Kamran and Myung Yung Jeong

Coatings 2019, 9(9), 573; https://doi.org/10.3390/coatings9090573 - 8 Sep 2019

Cited by 8 | Viewed by 4183

Abstract

Roll-to-roll ultraviolet (R2R-UV) imprinting is a low-cost and high-throughput method that includes the manufacturing of large-area functional films. However, the quality of the final product is obstructed by the bubble entrapment during the imprinting process. In this study, a multi-phase volume of fluid [...] Read more.

Roll-to-roll ultraviolet (R2R-UV) imprinting is a low-cost and high-throughput method that includes the manufacturing of large-area functional films. However, the quality of the final product is obstructed by the bubble entrapment during the imprinting process. In this study, a multi-phase volume of fluid (VOF) numerical model was used to remove bubble entrapment during the R2R imprinting process, which covered all parameters. This new modified numerical model with open-channel boundary conditions was based on the single zone that contains the direct contact of UV resin with the imprinting mold during the filling process. In addition, this model simulated the UV resin filling into microcavities at the preceding and succeeding ends of the imprinting mold. Different patterns of imprinting mold were considered to enhance the fidelity of R2R-UV imprinting for the comprehensive analysis. The experimental results validated through numerical simulations revealed that the bubble entrapment can be controlled by varying various parameters such as speed of the imprinting system, viscosity, contact angles, and pattern shape. The proposed model may be useful for a continuous bubble-free R2R imprinting process in industrial applications that includes flexible displays and micro/nano-optics. Full article

(This article belongs to the Special Issue Modelling and Simulation of Coating 2019)

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18 pages, 8001 KiB

Open AccessFeature PaperArticle

Curcumin-Containing Orthopedic Implant Coatings Deposited on Poly-Ether-Ether-Ketone/Bioactive Glass/Hexagonal Boron Nitride Layers by Electrophoretic Deposition

by Ranjot Singh Virk, Muhammad Atiq Ur Rehman, Muhammad Azeem Munawar, Dirk W. Schubert, Wolfgang H. Goldmann, Ján Dusza and Aldo R. Boccaccini

Coatings 2019, 9(9), 572; https://doi.org/10.3390/coatings9090572 - 8 Sep 2019

Cited by 50 | Viewed by 7009

Abstract

Electrophoretic deposition (EPD) was used to produce a multilayer coatings system based on chitosan/curcumin coatings on poly-ether-ether-ketone (PEEK)/bioactive glass (BG)/hexagonal boron nitride (h-BN) layers (previously deposited by EPD on 316L stainless steel) to yield bioactive and antibacterial coatings intended for orthopedic implants. Initially, [...] Read more.

Electrophoretic deposition (EPD) was used to produce a multilayer coatings system based on chitosan/curcumin coatings on poly-ether-ether-ketone (PEEK)/bioactive glass (BG)/hexagonal boron nitride (h-BN) layers (previously deposited by EPD on 316L stainless steel) to yield bioactive and antibacterial coatings intended for orthopedic implants. Initially, PEEK/BG/h-BN coatings developed on 316L stainless steel (SS) substrates were analyzed for wear studies. Then, the EPD of chitosan/curcumin was optimized on 316L SS for suspension stability, thickness, and homogeneity of the coatings. Subsequently, the optimized EPD parameters were applied to produce chitosan/curcumin coatings on the PEEK/BG/h-BN layers. The multilayered coatings produced by EPD were characterized in terms of composition, microstructure, drug release kinetics, antibacterial activity, and in vitro bioactivity. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the deposition of chitosan/curcumin on the multilayer coating system. The release of curcumin upon immersion of multilayer coatings in phosphate-buffered saline (PBS) was confirmed by ultraviolet/visible (UV/VIS) spectroscopic analysis. The antibacterial effect of chitosan/curcumin as the top coating was determined by turbidity tests (optical density measurements). Moreover, the multilayer coating system formed an apatite-like layer upon immersion in simulated body fluid (SBF), which is similar in composition to the hydroxyapatite component of bone, confirming the possibility of achieving close bonding between bone and the coating surface. Full article

(This article belongs to the Special Issue Electrochemical and Electrophoretic Deposition of Bioactive Coatings)

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9 pages, 2321 KiB

Open AccessArticle

Synthesis and Deposition of Ag Nanoparticles by Combining Laser Ablation and Electrophoretic Deposition Techniques

by Mònica Fernández-Arias, Massimo Zimbone, Mohamed Boutinguiza, Jesús Del Val, Antonio Riveiro, Vittorio Privitera, Maria G. Grimaldi and Juan Pou

Coatings 2019, 9(9), 571; https://doi.org/10.3390/coatings9090571 - 6 Sep 2019

Cited by 15 | Viewed by 5596

Abstract

Silver nanostructured thin films have been fabricated on silicon substrate by combining simultaneously pulsed laser ablation in liquid (PLAL) and electrophoretic deposition (ED) techniques. The composition, topography, crystalline structure, surface topography, and optical properties of the obtained films have been studied by energy [...] Read more.

Silver nanostructured thin films have been fabricated on silicon substrate by combining simultaneously pulsed laser ablation in liquid (PLAL) and electrophoretic deposition (ED) techniques. The composition, topography, crystalline structure, surface topography, and optical properties of the obtained films have been studied by energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-visible spectrophotometry. The coatings were composed of Ag nanoparticles ranging from a few to hundred nm. The films exhibited homogenous morphology, uniform appearance, and a clear localized surface plasmon resonance (LSPR) around 400 nm. Full article

(This article belongs to the Special Issue Surface Treatment by Laser-Assisted Techniques)

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10 pages, 2480 KiB

Open AccessArticle

Effect of Deposition Pressure on the Microstructure and Optical Band Gap of Molybdenum Disulfide Films Prepared by Magnetron Sputtering

by Chenyang Gong, Jianrong Xiao, Liwen Zhu, Zhiyong Wang and Songshan Ma

Coatings 2019, 9(9), 570; https://doi.org/10.3390/coatings9090570 - 6 Sep 2019

Cited by 13 | Viewed by 3305

Abstract

MoS₂ films were prepared via magnetron sputtering under different deposition pressures, and the effects of deposition pressure on the crystal structure, surface morphology, and optical properties of the resulting films were investigated. The results show that the crystallinity of the films first [...] Read more.

MoS₂ films were prepared via magnetron sputtering under different deposition pressures, and the effects of deposition pressure on the crystal structure, surface morphology, and optical properties of the resulting films were investigated. The results show that the crystallinity of the films first increases and then decreases with increasing pressure. The surface of the films prepared by magnetron sputtering is dense and uniform with few defects. The deposition pressure affects the grain size, surface morphology, and optical band gap of the films. The films deposited at a deposition pressure of 1 Pa revealed remarkable crystallinity, a 30.35 nm grain size, and a 1.67 eV optical band gap. Given the large electronegativity difference between MoS₂ molecules and weak van der Waals forces between layers, the MoS₂ films are prone to defects at different deposition pressures, causing the exciton energy near defects to decrease and the modulation of the surrounding band. Full article

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12 pages, 2437 KiB

Open AccessFeature PaperArticle

Biopolymer Coatings as Alternative to Modified Atmosphere Packaging for Shelf Life Extension of Minimally Processed Apples

by Stefania Volpe, Silvana Cavella and Elena Torrieri

Coatings 2019, 9(9), 569; https://doi.org/10.3390/coatings9090569 - 6 Sep 2019

Cited by 22 | Viewed by 3985

Abstract

The effect of caseinate/chitosan blend on the shelf life of minimally processed apples was studied. In the first phase of the work, the effect of the biopolymer coating on the respiration rate of the minimally processed apples was studied as function of gas [...] Read more.

The effect of caseinate/chitosan blend on the shelf life of minimally processed apples was studied. In the first phase of the work, the effect of the biopolymer coating on the respiration rate of the minimally processed apples was studied as function of gas composition (5%, 10%, 21% of O₂ with N₂ as balance at 5 °C) and temperature (5 °C, 10 °C at 5% of O₂ with N₂ as balance). In the second phase, the shelf life of the packed product was studied during storage at 5 °C. The gas composition (O₂%-CO₂%) in the package headspace, relative humidity, pH, hardness, color and antioxidant capacity of the product were monitored after 0, 1, 4, 7, 11, and 14 days. The coating effectively reduced respiration rate of the product when oxygen was over 10%. In the presence of the coating, the reduction of oxygen did not affect the respiration rate. At 5% of O₂, the respiration rate decreased by 50% by changing the temperature from 10 °C to 5 °C. Shelf life study showed that the chitosan—caseinate coating was able to preserve the mechanical properties and the antioxidant capacity of the product during storage by increasing the shelf life by 7 days to 11 days at 5 °C. Full article

(This article belongs to the Special Issue Edible Films and Coatings: Fundamentals and Applications)

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8 pages, 4953 KiB

Open AccessFeature PaperArticle

Structure of Highly Porous Silicon Dioxide Thin Film: Results of Atomistic Simulation

by F.V. Grigoriev, V.B. Sulimov and A.V. Tikhonravov

Coatings 2019, 9(9), 568; https://doi.org/10.3390/coatings9090568 - 5 Sep 2019

Cited by 13 | Viewed by 4607

Abstract

The high-energy glancing angle deposition of silicon dioxide films with alternation of deposition angle is studied using classical atomistic simulation. Both slow and fast alternations are investigated. The growth of vertical tree-like columns and chevron-like regular structures is demonstrated under fast and slow [...] Read more.

The high-energy glancing angle deposition of silicon dioxide films with alternation of deposition angle is studied using classical atomistic simulation. Both slow and fast alternations are investigated. The growth of vertical tree-like columns and chevron-like regular structures is demonstrated under fast and slow alternations, respectively. Due to high porosity, the density of the deposited silicon dioxide films is reduced to 1.3 ÷ 1.4 g/cm³. This results in reduction of the refractive index to 1.3, which agrees with known experimental data. For slow continuous substrate rotation, formation of a helical structure is demonstrated. Full article

(This article belongs to the Special Issue Design, Manufacturing and Measurement of Optical Film Coatings)

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10 pages, 4105 KiB

Open AccessEditor’s ChoiceArticle

Design and Preparation of a 6-Channel Fan-Shaped Integrated Narrow-Band Filter in the Mid-Infrared Band

by Yingbu Duan, Changlong Cai, Haifeng Liang, Tiantian Jia and Shujing Yin

Coatings 2019, 9(9), 567; https://doi.org/10.3390/coatings9090567 - 5 Sep 2019

Cited by 16 | Viewed by 3378

Abstract

A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. [...] Read more.

A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. Germanium and zinc sulfide were selected as the high and low refractive index film materials, respectively. Its average peak transmission reached 83.3%, the cut-off transmittance was less than 1%, and the full width at half maximum (FWHM) changed from 55 and 94 nm, and the central wavelength positioning accuracy error was less than 0.35%. Furthermore, transmittance was also calculated inversely, using the thickness of each layer of films, in order to deduce the reason of the decrease in peak transmittance. Thickness deviation of each layer and interface scattering contributed to the decrease of peak transmittance. Compared with the same type of products in the market, our filter showed better properties than that of some published and commercial filter. Full article

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11 pages, 6069 KiB

Open AccessArticle

Distribution of Al Element of Ti–6Al–4V Joints by Fiber Laser Welding

by Jiajia Zhang, Renzhi Hu, Shengyong Pang and Anguo Huang

Coatings 2019, 9(9), 566; https://doi.org/10.3390/coatings9090566 - 5 Sep 2019

Cited by 5 | Viewed by 3221

Abstract

In the process of laser welding, the uneven distribution of solute elements caused by element burning loss and flow of molten pool affects the quality of joints. In this paper, butt welding experiments were conducted on the 3 mm thick Ti–6Al–4V specimens with [...] Read more.

In the process of laser welding, the uneven distribution of solute elements caused by element burning loss and flow of molten pool affects the quality of joints. In this paper, butt welding experiments were conducted on the 3 mm thick Ti–6Al–4V specimens with different preset ratios of Al and Si powders by using 4 kW fiber laser. The distribution of Al solute element and its influence on the microstructure and mechanical properties of the final weld joint were investigated. The results showed that the self-diffusion of Al element and the flow of molten pool affects the alloy elements distribution in laser welding. And the microhardness of the welded joint with Ti–6Al–4V and 90% Al + 10% Si powders was significantly higher than that with only Ti–6Al–4V, with the difference of about 130HV. At the same time, in the joint with 90% Al and 10% Si powders, the acicular α’ size was finer, and basketweave microstructure was present as well. This research is helpful to better understand the distribution of Al solute element and its influence on the joint quality during laser welding of Ti–6Al–4V alloy, which provides a certain reference for improving the weld or surface properties of Ti–6Al–4V alloy during laser processing. Full article

(This article belongs to the Special Issue Laser Surface Modification of Metallic Materials)

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20 pages, 11585 KiB

Open AccessArticle

Microstructure and Microhardness of Ni/Al-TiB₂ Composite Coatings Prepared by Cold Spraying Combined with Postannealing Treatment

by Xiao Chen, Chengdi Li, Shunjian Xu, Yao Hu, Gangchang Ji and Hongtao Wang

Coatings 2019, 9(9), 565; https://doi.org/10.3390/coatings9090565 - 4 Sep 2019

Cited by 10 | Viewed by 3238

Abstract

Ni/Al-TiB₂ composite powders were deposited on the surface of 316L stainless-steel substrates by cold spraying at gas temperatures of 250 and 450 °C, respectively. Then, the as-sprayed coatings were annealed at 650 °C for 10, 20, and 30 h. The experimental results [...] Read more.

Ni/Al-TiB₂ composite powders were deposited on the surface of 316L stainless-steel substrates by cold spraying at gas temperatures of 250 and 450 °C, respectively. Then, the as-sprayed coatings were annealed at 650 °C for 10, 20, and 30 h. The experimental results showed that the average porosity of as-sprayed coating dropped from about 0.68% to 0.054% as the cold spraying gas temperature increased. The contents of Ni, Al, and TiB₂ in the as-sprayed coatings were different from that of the Ni/Al-TiB₂ composite powders. The main phase compositions of the as-sprayed Ni/Al-TiB₂ coatings were the same as those of composite powder, consisting only of pure Ni, Al, and TiB₂ phases. TiB₂ as a reinforced particle in the as-sprayed coating could obviously increase the microhardness of the coatings. NiAl₃ and Ni₂Al₃ intermetallic compounds were synthesized in situ in all of the annealed coatings, and the average contents of NiAl₃ and Ni₂Al₃ intermetallic compounds increased as the cold spraying gas temperature increased. The distribution of TiB₂ particle was changed as the annealing times increased, which changed from more comparative uniform distribution to accumulation. The average porosity of the annealed coatings increased as the annealing time increased. The microhardness of Ni/Al-TiB₂ coatings annealed at 650 °C for 10 h was increased remarkably due to the reinforcement role of TiB₂ particles and NiAl₃ and Ni₂Al₃ intermetallic compounds. Full article

(This article belongs to the Special Issue Coatings and Interfaces)

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17 pages, 7291 KiB

Open AccessArticle

Bifunctional TiO₂/AlZr Thin Films on Steel Substrate Combining Corrosion Resistance and Photocatalytic Properties

by Caroline Villardi de Oliveira, Akram Alhussein, Juan Creus, Frédéric Schuster, Michel L. Schlegel, Zhili Dong, Carmen Jiménez and Frédéric Sanchette

Coatings 2019, 9(9), 564; https://doi.org/10.3390/coatings9090564 - 3 Sep 2019

Cited by 9 | Viewed by 3718

Abstract

A novel multi-functional bilayer coating combining an anti-corrosion Al–Zr (4 at.% Zr) underlayer and an anti-biofouling TiO₂ top layer was deposited on high-speed steel (HSS) substrates. Al–Zr (4 at.% Zr) film, deposited by DC magnetron sputtering, which is a single phased supersaturated [...] Read more.

A novel multi-functional bilayer coating combining an anti-corrosion Al–Zr (4 at.% Zr) underlayer and an anti-biofouling TiO₂ top layer was deposited on high-speed steel (HSS) substrates. Al–Zr (4 at.% Zr) film, deposited by DC magnetron sputtering, which is a single phased supersaturated solid solution of Zr in Al, is used to provide sacrificial corrosion resistance of steels and TiO₂ is added as a top layer to induce photocatalytic activity and hydrophilic behavior which can generate antifouling properties in order to slow down the biofouling process. The top TiO₂ films, deposited at 550 °C by AACVD (aerosol-assisted chemical vapor deposition), consisting of anatase TiO₂ microflowers physically attached to the TiO₂ thin films present a high decomposition rate of Orange G dye (780 × 10⁻¹⁰ mol L⁻¹·min⁻¹). The enhanced photocatalytic performance is associated with the rough network and the presence of TiO₂ microflowers capable of supporting the enhanced loading of organic contaminants onto the film surface. Electrochemical tests in saline solution have revealed that bilayer films provide cathodic protection for the steel substrate. The Al–Zr/TiO₂ bilayer presents a lower corrosion current density of 4.01 × 10⁻⁷ A/cm² and a corrosion potential of −0.61 V vs. Ag/AgCl, offering good protection through the preferential oxidation of the bilayer and an increased pitting resistance. The proposed functionalized coating combining anticorrosion and photocatalytic properties is a promising candidate for an anti-fouling system in sea water. Full article

(This article belongs to the Special Issue Magnetron Sputtering Deposited Thin Films and Its Applications)

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32 pages, 9840 KiB

Open AccessFeature PaperArticle

Protection of Aluminum Alloy 3003 in Sodium Chloride and Simulated Acid Rain Solutions by Commercial Conversion Coatings Containing Zr and Cr

by Maja Mujdrica Kim, Barbara Kapun, Urša Tiringer, Gavrilo Šekularac and Ingrid Milošev

Coatings 2019, 9(9), 563; https://doi.org/10.3390/coatings9090563 - 3 Sep 2019

Cited by 28 | Viewed by 5943

Abstract

The morphology, composition and corrosion properties of commercial hexafluoro-zirconate trivalent chromium coatings (SurTec^® 650) deposited on chemically cleaned aluminum alloy 3003 were studied. The coatings were deposited at room temperature using different concentrations of SurTec^® 650 (10, 25 and 50 vol.%) [...] Read more.

The morphology, composition and corrosion properties of commercial hexafluoro-zirconate trivalent chromium coatings (SurTec^® 650) deposited on chemically cleaned aluminum alloy 3003 were studied. The coatings were deposited at room temperature using different concentrations of SurTec^® 650 (10, 25 and 50 vol.%) and different conversion times (90 s, 11 min and 18 min). Scanning electron microscopy with energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy and time-of-flight secondary ion spectrometry were employed to investigate the surface morphology, composition and thickness of uncoated and coated AA3003 samples. The morphology of the coating varied from uniform nodular to non-uniform and cracked; coatings were deposited at intermetallic particles and at the alloy matrix. The main constituents of conversion coatings were Zr(IV) and Cr(III) oxides; in addition to oxides, fluorides were also formed. The corrosion properties were investigated in two solutions: more aggressive sodium NaCl and less aggressive simulated acid rain. These commercial conversion coatings exhibited a good corrosion resistance but only after longer immersion in solution, i.e., 24 h. The results reveal an interesting behavior of zirconate-based coatings on aluminum-manganese alloy. Full article

(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)

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